Procédure : répertorier tous les nœuds dans une arborescence
Il est parfois utile de répertorier tous les nœuds d'une arborescence. Cela peut être utile pour savoir exactement comment une méthode ou une propriété affecte l'arborescence. L'une des manières de répertorier tous les nœuds sous forme textuelle consiste à générer une expression XPath qui identifie exactement et spécifiquement tout nœud dans l'arborescence.
Il n'est pas particulièrement utile d'exécuter des expressions XPath à l'aide de LINQ to XML. Les expressions XPath procurent des performances inférieures aux requêtes LINQ to XML, et les requêtes LINQ to XML sont beaucoup plus puissantes. Toutefois, XPath fonctionne bien comme méthode d'identification des nœuds de l'arborescence XML.
Exemple
Cet exemple illustre une fonction nommée GetXPath qui génère une expression XPath spécifique pour tout nœud de l'arborescence XML. Il génère des expressions XPath appropriées même lorsque des nœuds se trouvent dans un espace de noms. Les expressions XPath sont générées à l'aide de préfixes d'espaces de noms.
L'exemple crée ensuite une petite arborescence XML qui contient un exemple de plusieurs types de nœuds. Il itère ensuite au sein des nœuds descendants et imprime l'expression XPath pour chaque nœud.
Vous remarquerez que la déclaration XML n'est pas un nœud dans l'arborescence.
Voici un fichier XML qui contient plusieurs types de nœuds :
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<?target data?>
<Root AttName="An Attribute" xmlns:aw="https://www.adventure-works.com">
<!--This is a comment-->
<Child>Text</Child>
<Child>Other Text</Child>
<ChildWithMixedContent>text<b>BoldText</b>otherText</ChildWithMixedContent>
<aw:ElementInNamespace>
<aw:ChildInNamespace />
</aw:ElementInNamespace>
</Root>
Voici la liste des nœuds dans l'arborescence XML ci-dessus, exprimés en tant qu'expressions XPath :
/processing-instruction()
/Root
/Root/@AttName
/Root/@xmlns:aw
/Root/comment()
/Root/Child[1]
/Root/Child[1]/text()
/Root/Child[2]
/Root/Child[2]/text()
/Root/ChildWithMixedContent
/Root/ChildWithMixedContent/text()[1]
/Root/ChildWithMixedContent/b
/Root/ChildWithMixedContent/b/text()
/Root/ChildWithMixedContent/text()[2]
/Root/aw:ElementInNamespace
/Root/aw:ElementInNamespace/aw:ChildInNamespace
public static class MyExtensions
{
private static string GetQName(XElement xe)
{
string prefix = xe.GetPrefixOfNamespace(xe.Name.Namespace);
if (xe.Name.Namespace == XNamespace.None || prefix == null)
return xe.Name.LocalName.ToString();
else
return prefix + ":" + xe.Name.LocalName.ToString();
}
private static string GetQName(XAttribute xa)
{
string prefix =
xa.Parent.GetPrefixOfNamespace(xa.Name.Namespace);
if (xa.Name.Namespace == XNamespace.None || prefix == null)
return xa.Name.ToString();
else
return prefix + ":" + xa.Name.LocalName;
}
private static string NameWithPredicate(XElement el)
{
if (el.Parent != null && el.Parent.Elements(el.Name).Count() != 1)
return GetQName(el) + "[" +
(el.ElementsBeforeSelf(el.Name).Count() + 1) + "]";
else
return GetQName(el);
}
public static string StrCat<T>(this IEnumerable<T> source,
string separator)
{
return source.Aggregate(new StringBuilder(),
(sb, i) => sb
.Append(i.ToString())
.Append(separator),
s => s.ToString());
}
public static string GetXPath(this XObject xobj)
{
if (xobj.Parent == null)
{
XDocument doc = xobj as XDocument;
if (doc != null)
return ".";
XElement el = xobj as XElement;
if (el != null)
return "/" + NameWithPredicate(el);
// the XPath data model does not include white space text nodes
// that are children of a document, so this method returns null.
XText xt = xobj as XText;
if (xt != null)
return null;
XComment com = xobj as XComment;
if (com != null)
return
"/" +
(
com
.Document
.Nodes()
.OfType<XComment>()
.Count() != 1 ?
"comment()[" +
(com
.NodesBeforeSelf()
.OfType<XComment>()
.Count() + 1) +
"]" :
"comment()"
);
XProcessingInstruction pi = xobj as XProcessingInstruction;
if (pi != null)
return
"/" +
(
pi.Document.Nodes()
.OfType<XProcessingInstruction>()
.Count() != 1 ?
"processing-instruction()[" +
(pi
.NodesBeforeSelf()
.OfType<XProcessingInstruction>()
.Count() + 1) +
"]" :
"processing-instruction()"
);
return null;
}
else
{
XElement el = xobj as XElement;
if (el != null)
{
return
"/" +
el
.Ancestors()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
NameWithPredicate(el);
}
XAttribute at = xobj as XAttribute;
if (at != null)
return
"/" +
at
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
"@" + GetQName(at);
XComment com = xobj as XComment;
if (com != null)
return
"/" +
com
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
com
.Parent
.Nodes()
.OfType<XComment>()
.Count() != 1 ?
"comment()[" +
(com
.NodesBeforeSelf()
.OfType<XComment>()
.Count() + 1) + "]" :
"comment()"
);
XCData cd = xobj as XCData;
if (cd != null)
return
"/" +
cd
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
cd
.Parent
.Nodes()
.OfType<XText>()
.Count() != 1 ?
"text()[" +
(cd
.NodesBeforeSelf()
.OfType<XText>()
.Count() + 1) + "]" :
"text()"
);
XText tx = xobj as XText;
if (tx != null)
return
"/" +
tx
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
tx
.Parent
.Nodes()
.OfType<XText>()
.Count() != 1 ?
"text()[" +
(tx
.NodesBeforeSelf()
.OfType<XText>()
.Count() + 1) + "]" :
"text()"
);
XProcessingInstruction pi = xobj as XProcessingInstruction;
if (pi != null)
return
"/" +
pi
.Parent
.AncestorsAndSelf()
.InDocumentOrder()
.Select(e => NameWithPredicate(e))
.StrCat("/") +
(
pi
.Parent
.Nodes()
.OfType<XProcessingInstruction>()
.Count() != 1 ?
"processing-instruction()[" +
(pi
.NodesBeforeSelf()
.OfType<XProcessingInstruction>()
.Count() + 1) + "]" :
"processing-instruction()"
);
return null;
}
}
}
class Program
{
static void Main(string[] args)
{
XNamespace aw = "https://www.adventure-works.com";
XDocument doc = new XDocument(
new XDeclaration("1.0", "utf-8", "yes"),
new XProcessingInstruction("target", "data"),
new XElement("Root",
new XAttribute("AttName", "An Attribute"),
new XAttribute(XNamespace.Xmlns + "aw", aw.ToString()),
new XComment("This is a comment"),
new XElement("Child",
new XText("Text")
),
new XElement("Child",
new XText("Other Text")
),
new XElement("ChildWithMixedContent",
new XText("text"),
new XElement("b", "BoldText"),
new XText("otherText")
),
new XElement(aw + "ElementInNamespace",
new XElement(aw + "ChildInNamespace")
)
)
);
doc.Save("Test.xml");
Console.WriteLine(File.ReadAllText("Test.xml"));
Console.WriteLine("------");
foreach (XObject obj in doc.DescendantNodes())
{
Console.WriteLine(obj.GetXPath());
XElement el = obj as XElement;
if (el != null)
foreach (XAttribute at in el.Attributes())
Console.WriteLine(at.GetXPath());
}
}
}
Module Module1
<System.Runtime.CompilerServices.Extension()> _
Private Function StrCat(Of T)(ByVal source As IEnumerable(Of T), _
ByVal separator As String) As String
Return _
source.Aggregate(New StringBuilder(), _
Function(sb, i) sb _
.Append(i.ToString()) _
.Append(separator), _
Function(s) s.ToString())
End Function
<System.Runtime.CompilerServices.Extension()> _
Public Function GetXPath(ByVal xobj As XObject) As String
Dim retStr As String
If xobj.Parent Is Nothing Then
Dim doc As XDocument = TryCast(xobj, XDocument)
If doc IsNot Nothing Then
Return "."
End If
Dim el As XElement = TryCast(xobj, XElement)
If el IsNot Nothing Then
Return ("/" & NameWithPredicate(el))
End If
' The XPath data model does not include white space text nodes
' that are children of a document, so this method returns null.
Dim xt As XText = TryCast(xobj, XText)
If xt IsNot Nothing Then
Return Nothing
End If
Dim com As XComment = TryCast(xobj, XComment)
If com IsNot Nothing Then
If com.Document().Nodes().OfType(Of XComment)().Count() <> 1 Then
Return "/comment()[" & (com.NodesBeforeSelf().OfType _
(Of XComment)().Count() + 1) & "]"
Else
Return "/comment()"
End If
End If
Dim pi As XProcessingInstruction = TryCast(xobj, XProcessingInstruction)
If pi IsNot Nothing Then
If pi.Document.Nodes().OfType(Of XProcessingInstruction)(). _
Count() <> 1 Then
Return "/processing-instruction()[" & _
(pi.NodesBeforeSelf().OfType(Of XProcessingInstruction)() _
.Count() + 1) & "]"
Else
Return "/processing-instruction()"
End If
End If
Else
Dim el As XElement = TryCast(xobj, XElement)
If el IsNot Nothing Then
Return "/" & el.Ancestors().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)) _
.StrCat("/") & NameWithPredicate(el)
End If
Dim at As XAttribute = TryCast(xobj, XAttribute)
If at IsNot Nothing Then
Return "/" & at.Parent().AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & _
"@" & GetQName(at)
End If
Dim com As XComment = TryCast(xobj, XComment)
If com IsNot Nothing Then
retStr = "/" & com.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & "comment()"
If com.Parent().Nodes().OfType(Of XComment)().Count() <> 1 Then
retStr &= "[" & (com.NodesBeforeSelf().OfType(Of XComment)().Count() + 1) & "]"
End If
Return retStr
End If
Dim cd As XCData = TryCast(xobj, XCData)
If cd IsNot Nothing Then
retStr = "/" & cd.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & "text()"
If cd.Parent.Nodes().OfType(Of XText)().Count() <> 1 Then
retStr &= "[" & (cd.NodesBeforeSelf().OfType(Of XText)(). _
Count() + 1) & "]"
End If
Return retStr
End If
Dim tx As XText = TryCast(xobj, XText)
If tx IsNot Nothing Then
retStr = "/" & tx.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)).StrCat("/") & "text()"
If tx.Parent.Nodes().OfType(Of XText)().Count() <> 1 Then
retStr &= "[" & (tx.NodesBeforeSelf().OfType(Of XText)(). _
Count() + 1) & "]"
End If
Return retStr
End If
Dim pi As XProcessingInstruction = TryCast(xobj, XProcessingInstruction)
If pi IsNot Nothing Then
retStr = "/" & pi.Parent.AncestorsAndSelf().InDocumentOrder(). _
Select(Function(e) NameWithPredicate(e)). _
StrCat("/") & "processing-instruction()"
If pi.Parent.Nodes().OfType(Of XProcessingInstruction)().Count() <> 1 Then
retStr &= "[" & (pi.NodesBeforeSelf().OfType(Of XProcessingInstruction)(). _
Count() + 1) & "]"
End If
End If
End If
Return Nothing
End Function
Private Function GetQName(ByVal xe As XElement) As String
Dim prefix As String = xe.GetPrefixOfNamespace(xe.Name.Namespace)
If xe.Name.Namespace = XNamespace.None Or prefix Is Nothing Then
Return xe.Name.LocalName.ToString()
Else
Return prefix + ":" & xe.Name.LocalName.ToString()
End If
End Function
Private Function GetQName(ByVal xa As XAttribute) As String
Dim prefix As String = _
xa.Parent.GetPrefixOfNamespace(xa.Name.Namespace)
If xa.Name.Namespace = XNamespace.None Or prefix Is Nothing Then
Return xa.Name.ToString()
Else
Return prefix + ":" & xa.Name.LocalName
End If
End Function
Public Function NameWithPredicate(ByVal el As XElement) As String
If el.Parent IsNot Nothing AndAlso el.Parent.Elements(el.Name).Count() <> 1 Then
Return GetQName(el) + "[" & _
(el.ElementsBeforeSelf(el.Name).Count() + 1) & "]"
Else
Return GetQName(el)
End If
End Function
Sub Main()
Dim aw As XNamespace = "https://www.adventure-works.com"
Dim doc As XDocument = _
<?xml version='1.0' encoding="utf-8" standalone='yes'?>
<?target data?>
<Root AttName='An Attribute' xmlns:aw='https://www.adventure-works.com'>
<!--This is a comment-->
<Child>Text</Child>
<Child>Other Text</Child>
<ChildWithMixedContent>text<b>BoldText</b>otherText</ChildWithMixedContent>
<aw:ElementInNamespace>
<aw:ChildInNamespace/>
</aw:ElementInNamespace>
</Root>
doc.Save("Test.xml")
Console.WriteLine(File.ReadAllText("Test.xml"))
Console.WriteLine("------")
For Each obj As XObject In doc.DescendantNodes()
Console.WriteLine(obj.GetXPath())
Dim el As XElement = TryCast(obj, XElement)
If el IsNot Nothing Then
For Each at As XAttribute In el.Attributes()
Console.WriteLine(at.GetXPath())
Next
End If
Next
End Sub
End Module
Cet exemple génère la sortie suivante :
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<?target data?>
<Root AttName="An Attribute" xmlns:aw="https://www.adventure-works.com">
<!--This is a comment-->
<Child>Text</Child>
<Child>Other Text</Child>
<ChildWithMixedContent>text<b>BoldText</b>otherText</ChildWithMixedContent>
<aw:ElementInNamespace>
<aw:ChildInNamespace />
</aw:ElementInNamespace>
</Root>
------
/processing-instruction()
/Root
/Root/@AttName
/Root/@xmlns:aw
/Root/comment()
/Root/Child[1]
/Root/Child[1]/text()
/Root/Child[2]
/Root/Child[2]/text()
/Root/ChildWithMixedContent
/Root/ChildWithMixedContent/text()[1]
/Root/ChildWithMixedContent/b
/Root/ChildWithMixedContent/b/text()
/Root/ChildWithMixedContent/text()[2]
/Root/aw:ElementInNamespace
/Root/aw:ElementInNamespace/aw:ChildInNamespace